Automatic circuit breaker



Aug. 6, 1940. J. sAcHs AUTOMATIC CIRCUIT BREAKER Filed Feb. 27.. 1939 1771 5 17: 0] Jaagph 5a 0275 Patented Aug. 5, 1940 amete RCUHT BREAKER necticut Application February 2'3, 1939, Serial No. 258,?03

2 Claims.

This invention relates to automatic circuit breakers of the type wherein the electro-responsive means comprises a bi-metallic element adapted upon being heated and deflected to cause the 5 automatic opening of the circuit. The invention is applicable to a circuit breaker of this type wherein the bi-metallic element is bodily movable with the movable contact as exemplified in my reissued Patent No. 20,018 entitled Automatic circuit breaker.

With any such automatic circuit breaker utilizing a bi-metallic strip as the sole electroresponsive means for effecting opening of the circuit, there is an appreciable delay in the opening by reason of the time required for heating and deflecting the strip. In some instances it is found desirable to provide for a delay in opening somewhat greater than that ordinarily obtained, and it is the general object of the present invention to provide for such increased delay.

In accordance with the invention 1 provide not only the usual current carrying bi-metallic strip but also a second strip which does not carry current, but which is closely adjacent the first strip so as to receive heat therefrom. This second strip upon being heated acts mechanically on the first strip to increase the deflection thereof, but this mechanical action of the second strip upon the first is necessarily delayed on account of the time required for the heating of the second strip.

In the accompanying drawing I have shown one suitable embodiment of the invention, and I have selected for illustration the mechanism shown in my co-pending application for Automatic circuit breakers, Serial No. 152,020 filed July 6, 1937. It will be understood however, that I do not limit myself to the mechanism shown and the drawing is intended for illustrative purposes only and is not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

Fig. 1 is a front view of a circuit breaker embodying the invention, with certain parts broken away to show other parts more clearly.

Fig. 2 is a vertical sectional View taken along the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary vertical sectional view similar to Fig. 2, but showing the parts in the positions which they assume upon automatic opening while the handle is held in closed-circuit position. 7

(ill. 20ll116) of the parts including the handle in open circuit positions.

A main base or housing i is provided which supports the circuit breaker mechanism and all of the conducting parts. As shown this is an integral structure comprising a rear wall I and two forward projecting side walls I, l which are spaced apart and which are identical in construction. The housing has a front cover 2 which may be of metal, an insulating sheet 3 being interposed between the cover and the housing. The cover 2 and sheet 3 will be referred collectively as constituting the front cover plate. The front cover plate is held in place by screws 4, t which also serve to secure the housing i to a metallic supporting plate 5. The supporting plate 5 is secured by suitable means, such as screws E, ii, to the rear wall of an outer metallic casing 'l. The casing 17 has an openable front cover 8 secured by screws 9, 9, the said cover preferably having a central depressed portion 8" closely adjacent the housing cover 2.

A stationary main contact it is provided which is carried by a resilient conductor ii located near the upper end of the base or housing l and held in place by a, screw l2. A nut [13 on the screw l2 cooperates with the conductor H to form a wire terminal. A stationary conductor M is secured to the base or housing i near the lower end thereof by means of a screw it. A nut IS on the screw i5 cooperates with the conductor It to constitute a wire terminal.

A mechanism supporting frame is positioned between the main side walls I, l of the housing, this frame comprising two similar plates l1, l1. The frame is so engaged by the housing that rearward movement thereof is prevented, and for this purpose the plates I1, I! have lateral projections H H which are seated in notches in the side walls of the housing and which prevent rearward movement of the frame. Forward movement of the frame is prevented by the front cover plate when the said plate is in place.

Directly connected electrically with the stationary conductor M is a flexible conductor l8. For making and breaking the circuit between the contact If! and the conductors i4 and Hi there is provided a contact carrying member which is movable about a fixed axis. The said contact member comprises a conducting element or bar 89 which carries a movable contact '20 adapted to engage and disengage the stationary contact ill. The contact member also comprises an arm 2i which is in generally parallel relationship with the bar l9 and which is formed of sheet metal bent to a U-shape to provide two similar legs. The conducting bar I!) has an angularly bent portion Ill which directly engages the transverse portion of the operating arm between the two legs thereof, the last said portions beingheld together by a rivet 22.

The contact member is pivotally mounted between the plates l1, I! of the frame, by means of a transverse bearing member 23. The bearing member 23 is supported in insulating bushings 24 which insulate the contact member from the supporting frame. Surrounding the member 23 is a coil spring 25 which engages the arm 2| and also engages an insulating member 26 extending transversely between the frame side plates, this spring thus serving to bias the contact member in the contact disengaging direction. Projections ll on the frame plates serve to engage the legs of the arm 2| and thus limit forward movement of the contact member.

A handle or operating member 21 is pivotally supported on the supporting frame by means of a pivot pin 28 extending transversely between the frame side plates. The forward or handle portion of the operating member projects through suitable openings in the front cover plate of the housing and in the front cover 8 of the outer casing. The operating member 21 is biased in the clockwise direction by a spring 29.

In order 'that the operating member 21 may operate the contact member, there is provided a connecting mechanism which is controlled by means of a bi-metallic element 30 bodily movable with the contact member and serving in and of itself as a latch which cooperates directly with an actuator 3| mechanically connected with the operating member.

The actuator 3| is carried directly upon the arm 2| of the contact member so as to move bodily therewith, and it is pivotally mounted at 32 between the two legs of the said arm. The actuator 3| is insulated from the arm 2| by means of suitable insulating bushings (not shown) which surround the pivot pin 32. The actuator 3| extends rearward and projects through a slot in the conducting arm l9.

A link 33 is pivotally connected with the operating member 21 at 34 and with the actuator 3| at 35. With the parts in the normal closed-circuit position as shown in Fig. 2, the pivotal axis at 34'is above a straight line connecting the pivotal axes at 28 and 35, the operating member itself thus cooperating with the link 33. to form a normally locked toggle. A member 36 extending l9. It may be held by the same rivet 22 which connects the conducting bar IS with the operating arm 2|. The before-mentioned flexible conductor l8 is electrically connected with the bimetallic latch 30 near the upper latching end thereof. This connection may be effected by brazing.

With the circuit breaker in closed-circuit position as shown in Fig. 2 it will be apparent that electrical connection is established from the statlonary contact l to the movable contact 20, thence through the-conducting bar l9 and the rivet 22 to the bi-metallic latch 3|), and thence through the flexible conductor I 8 to the stationary conductor l4.

As already stated, the contact member is biased in the circuit-opening direction by means of the spring 25, and the operating member is biased in theclockwise or circuit-opening direction by means of the spring 29. However, actual movement in the circuit-opening direction is normally prevented by reason of the described toggle relationship between the operating member itself and the link 33, it being understood that the latch 30 normally holds the actuator 3| from relative movement in the clockwise direction.

Normally the operating member 21- may be moved to move the contact member and thus open or close the circuit. During such normal movements the latch 30 remains engaged with the actuator 3| If the handle or operating member 21 be held in its closed-circuit position as shown in Figs. 2 and 3 and if an abnormal current condition such as an overload is attained, the bimetallic latch 30 is automatically deflected rearward as indicated in Fig. 3 so as to disengage and release the actuator 3|.

When the actuator is no longer held by the latch 3|], the entire contact member is' moved by the spring 25 to its open-circuit position as shown in Fig. 3, the actuator 3| and the link 33 assuming the relative positions shown in that figure. If the operating member be released after the parts have moved to the relative positions shown in Fig.- 3, the spring 29. moves the operating member to the position shown in Fig. 4, this in turn moving the link 33 and the actuator 3| to the positions shown in that figure. The actuator is thus restored to engaged or eng ageable relationship with the bi-metallic latch 30.

The operation has been described as it occurs when the handle is first held and then released. Ordinarily, however, the operating member is not held and it starts to'move to its open-circuit position as soon as the actuator has moved far enough in the clockwise direction to break the locking relationship between the operating member and the link 33. All of the parts thus move practically instantaneously to the position shown in Fig. 4, the actuator being immediately restored to engaging relationship with the latch. As soon as the latch has cooled sufficiently the operating member can be moved to again close the circuit.

In order to adjust the bi-metallic latch 30 for purposes of calibration it may be desirable to provide an adjusting screw 31 extending through a hole in the said latch and into a-threaded hole in an extension 2 l of the operating arm. It will be apparent that by adjusting the screw 31 the latch 30 may be moved within'c'ertain narrow limits so as to be adapted to release the actuator upon the attainment of predetermined overload condition.

In accordance with the present invention I not only provide a bi-metallic element such as I terial such as mica. As shown the bi-metallic element 38 has an angularly bent portion 38 between the portions 30 and Hi all of the said portions being held by the said rivet 22. The bi-metallic element 38 and the mica. sheet 3t have relatively large holes therein to provide ample clearance for the adjusting screw-31.

Let it be assumed that the circuit breaker is subjected to a moderate overload which the bimetallic latch 30 would carry indefinitely without sufficient deflection to cause release of the actuator 3!. However, the latch 30 is heated to some extent and the heat thereof is slowly transmitted to the bi-metallic element 38. The element 38 is of such character that it has a greater amount oi deflection for a given temperature, and therefore the element 38 upon finally becoming heated deflects rearward and acts mechanically on the latch 30 to increase the deflection thereof. The latch 30 upon being thus additionally deflected releases the actuator 3| and the circuit is opened in the manner already described.

What I claim is:

1. In combination in an automatic circuit breaker, a contact biased for movement to break the circuit, releasable mechanism normally holding the contact in closed-circuit position and including a bi-metallic element held at one end and capable of deflection when heated to cause the other end to relatively move and thereby efiect the release of the mechanism, means for connecting the bi-metallic element in the circuit to cause the heating thereof as the result of excess current conditions therein, and a second bimetallic element positioned immediately adjacent the first element but mounted and arranged so as not to carry current, the said second element being heated and deflected solely by heat transmitted from the first element and the second element when so heated and deflected acting upon the first element to increase the defiection thereof.

2. In an automatic circuit breaker, the combination of a stationary contact, a movable contact member having a contact adapted to engage and disengaged the stationary. contact, the said contact member being biased for movement toward its open-circuit position and being normally mechanically held against such movement, a thermostatic bi-metallic element supported upon and bodily movable with the contact member and connected in the circuit to be heated upon the attainment of an abnormal current condition therein and thus deflected so as to mechanically release the contact member and permit it to automatically move to open-circuit position, and a second bi-metallic element positioned immediately adjacent the first element and bodily movable therewith but mounted and arranged so as not to carry current, the said second element being heated and deflected solely by heat transmitted from the first element and the second element when so heated and deflected acting upon the first element to increase the deflection thereof.

JOSEPH SACHS. 

